Plastic fan hub

ABSTRACT

Disclosed is a hub formed of plastic which carries a fan spider or a blower wheel and has a central bore to accommodate a motor shaft. A cavity is formed in the hub and accommodates a resilient leaf which is threaded on a shaft-engaging set screw extending radially into the central bore. Tightening the set screw on the shaft distorts the resilient member and the internal restoring force thereby exerted by the resilient member holds the hub locked on the shaft despite the normal cold-flow or creep of the hub material.

United States Patent Wooden [541 PLASTIC FAN HUB [75] lnventor: John A. Wooden, Oaklandon, Ind.

[73] Assignee: Brookside Corporation, McCordsville,lnc.

[22] Filed: Feb. 24, 1971 [21] Appl. No.: 118,379

[52] US. Cl. ..4l6/l34, 416/244, 287/5208 [51] Int. Cl ..F04d 29/20 [58] Field oiSearch...4l6/134, 244, 241 A; 64/27 R, 64/27 NM; 287/5208 [5 6] References Cited UNITED STATES PATENTS 1,309,675 7/1919 Young et al. ..287/52.08 2,322,803 6/1943 Koch ..287/52.08 X 2,335,394 11/1943 Devore et al. ..4l6/24l A 2,614,872 10/1952 Heidegger et al. ..287/52.08

1 Jan. 2, 1973 3,021,049 2/1962 Settle ..4l6/244 X 3,319,939 5/1967 Rogenski ..416/227 X 3,376,057 4/1968 Van Buren ..4l6/244 X 3,600,013 8/197] Doering ..287/52.08

Primary Examiner-Everette A. Powell, Jr. Attorney-Woodard, Weikart, Emhardt & Naughton [57] ABSTRACT Disclosed is a hub formed of plastic which carries a fan spider or a blower wheel and has a central bore to accommodate a motor shaft. A cavity is formed in the hub and accommodates a resilient leaf which is threaded on a shaft-engaging set screw extending radially into the central bore. Tightening the set screw on the shaftdistorts the resilient member and the internal restoring force thereby exerted by the resilient member holds the hub locked on the shaft despite the normal cold-flow or creep of the hub material.

5 Claims, 3 Drawing Figures PLASTIC FAN nun BACKGROUND OF THE INVENTION In order to minimize the cost of fabrication and assembly of air moving elements such as fans and blower wheels, the use of molded plastic in forming the fan spider or blower wheel, the bladed element, has greatly increased. It is desirable that such plastic fan elements be supported on plastic hubs to facilitate bonding of the fan element and hub, to maintain the light overall weight of the complete assembly and to retain the cost advantage of molded plastic components over metal hubs. Plastic hubs for locking fans or blower wheels on motor shafts have, however, encountered the difficulty that the plastic material from which the hub is molded tends to cold-flow or creep when under prolonged stress and the fan hubs, as a result, eventually loosen on the shaft and failure or noisy operation of the fan or blower assembly results.

The hub embodying the-concept of the present invention utilizes a resilient member whose restoring force, when deformed by tightening a set screw against the motor shaft accommodating the hub, serves to compensate for any weakening of the hub-to-shaft lockingforce caused by creep of the material'from .which the plastic hub is molded. The hub, and hence the air moving element carried by it, can be loosened and easily removed from the shaft in the field for servicing and repair of the air moving element or to provide access to associated equipment. The construction also reduces considerably the variation in'the actual thrust of the set screw against the shaft and the consequent variation in holding power. Set screws are normally set by the assembler to a certain predetermined torque. Variations in threads, finishes, and lubricants can actually cause a many-fold variation of the amount of thrust caused by a set or predetermined torque. This construction minimizes this problem because the physical flattening of the resilient member will give the assembler a definite, easily visible and felt reference or limit point, resulting in less thrust force variation.

BRIEF DESCRIPTION OF. THE DRAWINGS FIG. 1 is an end view of a hub embodying the present invention and shown in place upon a motor shaft.

FIG. 2 is a top plan view of the hub shown in FIG. 1 but with the set screw and resilient element omitted.

FIG. 3 is a sectional view taken generally along the line 3-3 of FIG. 2, with a fan spider in place on the hub, the fan spider being shown fragmentarily only.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, a plastic hub, indicated generally at is molded or otherwise formed to pro vide a central bore 11 having atruncated circular configuration, as will be evident from FIG. 1,,and which is adapted to accommodate a shaft 12 which may be a conventional motor shaft.

Intermediate its ends, the hub 10 is provided with a radially extending. flange 13 as may be seen in FIG. 3. The portion of the hub body adjacent the flange 13 accommodates a driven element such as a fan spider or the end plate of a centrifugal blower wheel fragmentarily-indicated at 14. The fan element 14 may be rigidly attached at the engaging surfaces 16 to the hub by solvent or adhesive bonding, or by any other suitable As may be seen in FIG. 3, the cavity 17 is open at one end and accommodates a resilient element 2 (FIG. 1 which has a central aperture with portions of the resilient element struck downwardly and given a contour so as to receive the threaded circumference of the set screw 22. The set screw 22 extends freely through registering apertures 23 and 24 in the upper and lower walls of the cavity 17. In unstressed, normal condition the resilient member 21 has a dished or concavo-con vex configuration as shown in FIG. I. i j r In operation, the fully 'assemblied hub, carrying an air moving element (not shown .in FIG. I) may be slipped upon a motor shaft 12 and the set screw 22 tightened against the flat segment of the shaft. Further turning of the set screw serves to move the central portion of the resilient member 21 upwardly as viewed in FIG. 1, flattening the resilient member against the upper wall of the cavity 17 and storing energy in the deformed or flattened resilient member. The restoring force in the distorted resilient member serves to urge the set screw 22 downwardly against the shaft 12 and is sufiicient to maintain a stronglocking pressure by the set screw against the shaft despite normal creep or cold-flow of the material of the hub which would otherwise serve to decrease the pressureexerted .by the set screw on the shaft. Theforce stored in the deformed resilient member 21 thus serves to compensate for creep of the material of the plastichub and maintains the hub locked onthe shaft.

It will be noted that the hub of the present invention utilized relatively simple and readily available components such as the set screw and resilient member. Further, it will be understood,-that while a fan or other driven element is described being attached to the hub at surfaces 16, the hub might be integrally molded with body being formed to provide a cavity extending in depthv parallel to the longitudinal axis of said central bore and extending in width transverse to the longitudinal axisof said central bore, a set screw extending radially from said central bore and accommodated in registering apertures in the walls of said cavity, and a resilient member threaded on said set screw and I disposed within said cavity, said resilient member hav-- said cavity as the inner end of said set screw is moved to,

locking engagement with a shaft accommodated within said central bore, the restoring force exerted by the distorted resilient member serving to maintain the locking engagement of said set screw with the bore-accommodated shaft despite the normal creep of the material from which said hub is formed.

2. A plastic hub as claimed in claim 1 in which said cavity is substantially rectangular and said resilient 4 body to permit insertion of said resilient member into said cavity subsequent to theiforming of said hub.

4, A plastic hub as claimed in claim I in'which a radial annular flange extends from said hub body intermediate the body ends to provide a surface towliich'a driven element can be attached. I v

5. A plastic hub as claimed in claim 1 in which "said central bore in the hub body is of truncated circular configuration in cross-section with the flat side facingsaid cavity and in which one of said reg'istermg set screw accommodating apertures intersects-said flat side ofthe central bore;

es o se 

1. A plastic hub for mounting a driven element such as a fan, blower wheel or the like on a motor shaft, said hub comprising a body having a central bore therethrough adapted to receive a motor shaft, said body being formed to provide a cavity extending in depth parallel to the longitudinal axis of said central bore and extending in width transverse to the longitudinal axis of said central bore, a set screw extending radially from said central bore and accommodated in registering apertures in the walls of said cavity, and a resilient member threaded on said set screw and disposed within said cavity, said resilient member having a dished configuration adapted to be distorted into a flattened configuration by engagement with a wall of said cavity as the inner end of said set screw is moved to locking engagement with a shaft accommodated within said central bore, the restoring force exerted by the distorted resilient member serving to maintain the locking engagement of said set screw with the boreaccommodated shaft despite the normal creep of the material from which said hub is formed.
 2. A plastic hub as claimed in claim 1 in which said cavity is substantially rectangular and said reSilient member extends substantially to the outer side margins of said cavity and is flattened against the cavity wall nearest the periphery of said hub as said set screw is moved into locking engagement with the bore-accommodated shaft.
 3. A plastic hub as claimed in claim 1 in which said cavity is open across its width at the end of said hub body to permit insertion of said resilient member into said cavity subsequent to the forming of said hub.
 4. A plastic hub as claimed in claim 1 in which a radial annular flange extends from said hub body intermediate the body ends to provide a surface to which a driven element can be attached.
 5. A plastic hub as claimed in claim 1 in which said central bore in the hub body is of truncated circular configuration in cross-section with the flat side facing said cavity and in which one of said registering set screw accommodating apertures intersects said flat side of the central bore. 